JPH10197872A - Alignment treatment method for alignment film of liquid crystal display element - Google Patents

Abstract

(57) [Problem] To provide an alignment treatment method for an alignment film, which is easy to carry out while maintaining the cleanliness of the process. SOLUTION: A step of forming an alignment film made of a photo-alignment polymer on a substrate, and irradiating the substrate with a surface provided with the alignment film using light refraction means for emitting light in multiple directions. Stages. As a result, the alignment film can be oriented by only one light irradiation, so that the manufacturing process can be simplified and the productivity can be improved as compared with the conventional case.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for aligning an alignment film of a liquid crystal display device, and more particularly to a method for aligning an alignment film which is easy to carry out while maintaining the cleanliness of the process.

[0002]

2. Description of the Related Art An ordinary liquid crystal display device has the following structure.

[0003] In addition to being opposed at a predetermined interval,
A transparent electrode layer is formed on the lower substrate, and an alignment film (alignment layer) for aligning liquid crystal is formed on the transparent electrode layer.
yer) is formed. A liquid crystal layer is formed between the alignment films on the upper and lower substrates.

In the above-described liquid crystal display device, the arrangement of the liquid crystal changes depending on whether or not an external voltage is applied, and external light flowing into the liquid crystal display device is blocked and transmitted by such a change in the arrangement of the liquid crystal. That is, when a voltage is applied to the transparent electrode layer, an electric field is formed in the liquid crystal layer. As a result, the liquid crystal is aligned in a certain direction, and the light flowing into the liquid crystal of the display device is blocked or transmitted depending on whether the liquid crystal is aligned, and an image is realized on the display screen film.

In such a liquid crystal display device, characteristics such as light transmittance, response speed, viewing angle, and contrast are determined according to the alignment characteristics of liquid crystal molecules. Therefore, it is very important to control the alignment of liquid crystal molecules uniformly.

[0006] The uniform alignment state of the liquid crystal simply raises the liquid crystal,
It is difficult to obtain simply by interposing between the lower substrates. Therefore, as can be seen from the structure of the liquid crystal display element, an alignment film is formed on the transparent electrode layer.

Generally, an alignment film has a function of aligning liquid crystal molecules by being subjected to an alignment treatment at the last stage in the manufacturing process. A rubbing method has been frequently used as such an alignment treatment method. That is, after forming an alignment layer made of a polymer on a substrate, the alignment layer is rubbed with a special type of cloth.

As a recently developed method, there is an alignment method using light (optical alignment method). The photo-alignment method will be described with reference to FIG.

First, an alignment film 12 made of a photo-alignable polymer is formed on a substrate 11. When the alignment film 12 is locally irradiated with light using the photomask 13, the photo-alignment polymer of the alignment film in the corresponding region is arranged. Thereafter, light should be irradiated again to the other region of the alignment film using the photomask 13.

[0010] Of the above-mentioned alignment treatment methods, the rubbing method is easy to carry out and the process is simple, so that a large area of liquid crystal can be aligned at one time. However, fine particles or fibrous materials may be detached from the special-shaped cloth used at the time of rubbing and contaminate the alignment film. The orientation may not be improved depending on the material of the orientation film, and there is a problem that the thin film transistor is damaged by static electricity generated at the time of rubbing.

In the photo-alignment method, the cleanliness of the process is maintained without generating static electricity. However, as described above, the light irradiation step using the photomask should be repeated several times, and thus there is a problem that the manufacturing is troublesome.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a method of aligning an alignment film which is easy to implement while maintaining the cleanliness of the process.

[0013]

In order to achieve the above object, the present invention provides a method of forming an alignment film made of a photo-alignment polymer on a substrate, and using a light refraction means for emitting light in multiple directions. Irradiating light to a surface of the substrate provided with the alignment film.

As the light refracting means, it is preferable to use a polygonal pyramid such as a triangular pyramid or a quadrangular pyramid, a polygonal column such as a triangular prism or a quadrangular prism, or a prism having a truncated polygonal pyramid.

The photo-alignable polymer is not particularly limited, and may be polyvinyl cinnamate,
Polyvinyl methoxycinnamate
innamate), traditional photopolymers like polyimide
It is preferable to use (photopolymer).

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An alignment treatment method for an alignment film according to the present invention will be described with reference to FIG.

First, an alignment film 22 made of a photo-alignable polymer is formed on a substrate 21. Light is irradiated by using a polygonal prism 23 as a light refracting means. Here, the prism 23 has a shape capable of refracting incident light in multiple directions.

When light is irradiated using such a polygonal prism, the light passes through the prism 23 and irradiates the alignment film 22 at a fixed angle to orient the alignment film. FIG.
, The solid line indicates the path of the incident light, and the dotted line indicates the path of the light passing through the prism.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples.

<Example> After an ITO electrode was coated, polyvinyl cinnamate and N
After applying a composition containing -methylpyrrolidone, the composition was dried to form an alignment film. Then, after placing a quadrangular pyramid-shaped prism on the upper part of the substrate, ultraviolet rays of about 365 nm were irradiated.

An empty cell was manufactured by bonding two upper and lower substrates while maintaining a constant gap using a spacer. Thereafter, liquid crystal was injected into the empty cell to complete a liquid crystal display device.

Comparative Example After the ITO electrode was coated, a composition containing polyvinyl cinnamate and N-methylpyrrolidone was applied on a lower glass substrate, and then dried to form an alignment film.

Then, after a photomask was positioned on one side of the substrate or above a certain area, ultraviolet rays of about 365 nm were irradiated. Next, after a photomask was positioned on the other side surface or another region of the substrate, ultraviolet rays were irradiated in a different direction from the above. The light irradiation process was repeated to orient the alignment film.

An empty cell was manufactured by joining two upper and lower substrates while maintaining a constant gap using a spacer. Thereafter, liquid crystal was injected into the empty cell to complete a liquid crystal display device.

As described above, in the case of the comparative example, since the ultraviolet irradiation process using the photomask should be repeatedly performed, it is very troublesome. On the other hand, in the case of the embodiment, since the alignment treatment can be performed on the alignment film with only one irradiation of the ultraviolet ray, the alignment treatment process is very simple.

[0026]

According to the present invention, when the alignment film is aligned,
Since the alignment film can be oriented by only one light irradiation, the manufacturing process can be shortened as compared with the conventional case, and the productivity is improved.

[Brief description of the drawings]

FIG. 1 is a schematic view illustrating a photo-alignment method of an alignment film according to the related art.

FIG. 2 is a schematic view illustrating one photo-alignment method of an alignment film according to the present invention.

[Explanation of symbols]

 11 --- substrate 12 --- alignment film 13 --- photomask 21 --- substrate 22 --- alignment film 23 --- prism

Claims (2)

[Claims] Forming an alignment film made of a photo-alignable polymer on a substrate, and irradiating light to a surface of the substrate provided with the alignment film by using light refraction means for emitting light in multiple directions. And a step of performing alignment treatment of the alignment film. 2. The method according to claim 1, wherein the light refracting means is a polygonal pyramidal prism.